The present invention is directed to a process for controlling the strip run of a metal strip through a treatment device.
The treatment device is a floating furnace through which the metal strip is guided horizontally on air cushions, where the strip run is controlled inside the floating furnace. In conventional plants, the strip is usually guided by means of movable guide rolls that can be used to correct the strip run. However, a strip guiding device of this type is problematical in annealing furnaces because the guide rolls can damage the soft-annealed metal strip. Thus, the strip is currently guided by means of guide rolls arranged before and after the furnace.
The metal strip is conveyed through the furnace and along the subsequent cooling line while floating on air cushions. Modern horizontal floating furnaces including a cooling line can easily reach lengths in excess of 130 meters. Even if the metal strip is guided into the floating furnace in the center, there may be lateral drift inside the furnace. If the soft strip touches the wall of the furnace, it will be damaged. One possible solution would be to build the furnace much wider than the metal strip so that it can drift to the side to a certain extent without touching the walls. However, this would not make good use of the furnace capacity. Another possibility would be to mount mechanical limits on the furnace wall, but these limits could bend the sides of the metal strip upwards.
DE 1205291 describes a device for avoiding contact with the wall by means of a specially designed air cushion underneath the strip that centers the metal strip automatically. However, the strip run cannot be influenced actively.